Technical Field
The following embodiments relate to communication session control between a plurality of apparatuses connected via a network.
Description of the Related Art
In recent years, a technology has become widely commercially available in which multimedia data such as a moving image and audio is distributed and viewed via streaming using a communication protocol called the Real-time Transport Protocol (RTP).
RTP is a protocol for transferring data mainly such as audio or a moving image and is defined as RFC3550 by the Internet Engineering Task Force (IETF).
RTP is an upper layer protocol of the User Datagram Protocol (UDP), which is a connectionless protocol. In the case where communication is performed using RTP by packetizing moving image data or audio data, RTP packets flowing in a network are generally called stream data or a media stream.
As a protocol for performing control using RTP such as for starting or ending a media stream, the Real Time Streaming Protocol (RTSP) is generally known. RTSP is defined as RFC2326 by IETF.
For a communication session controlled by RTSP, in the case where no messages have been transmitted for a predetermined time period from a client that receives stream data to a server, which is a transmission source, it may be considered that the communication session has timed out and the server may terminate the session.
In the case where the communication session is desired to be continued, the communication session may be continued by sending a message from the server before the predetermined time period elapses. Such a system for continuing a communication session is also called a “keepalive”.
In RTSP, when a communication session is started, a server notifies a client of a time period after which a communication session times out (hereinafter referred to as a timeout time period). The client may cause the transmission session to be continued by transmitting an arbitrary RTSP command to the server before the timeout time period elapses.
PCT Japanese Translation Patent Publication No. 2005-526294 has disclosed, as a way in which a communication session is continued, a communication system using a protocol called the Real-Time Transport Control Protocol (RTCP) in addition to RTSP.
RTCP is used in combination with RTP. RTCP is a protocol for performing flow control or transferring information between a sender and a receiver, and is defined as RFC3550 by IETF.
In RTCP, in order that a client side notifies a server side of the status of communication, a type of packets called receiver report (hereinafter referred to as RR) is used.
Hitherto it has been known a method for causing a server to continue a communication session through periodic notification of an RR packet from a client to a server.
However, in the case where a communication session is managed using a plurality of communication procedures (communication protocols), a communication session with a client that is not authenticated by a server may be established or continued.
For example, in the case where a first protocol that supports a client authentication function and a second protocol that does not support the client authentication function are used together, the following issues arise, the client authentication function being a function through which authentication of a client is performed. That is, a communication session with a client that is not authenticated by a server may be established or continued.
For example, when a communication session is established or retained between a server and a client, RTSP supports the client authentication function performed by the server.
In contrast, RTCP does not support the client authentication function, which is performed by a server. Thus, in the case where a communication session is continued through periodic notification of an RR packet from a client to a server as in the above-described conventional example, authentication of the client is not required.
Thus, as a result of authentication of a client in communication using RTSP, even though it is determined by the server that a communication session is not continued with the client, communication may be continued with the client through communication using RTCP.
In this manner, there may be the case where secure communication is not possible.
According to the following embodiments, more secure communication session control may be realized.